Receiver tuning control



0d. 8, 1940. E. L Qumy RECEIVER TUNING CONTROL Fim Jan. s, 193s 6 Sheets-Sheet 1 o@ s, -1940. E, J. QUINBY 2,217,293

RECEIVER TUNING CONTROL Filid Jan. 3, 1936 6 Sheets-Sheet 2 INVENTOR E D W//V J. U/A/BY Oct. 8, i949. E, J, QUlNBY @217,293

RECEIVER TUNING CONTROL Fi Jin. 3. 1936 'G SheH'Ls-Sheet 3 INVENTOR 50W/N J. OU//VBY y ATTORNEY Oct. v8, 1940, E, J. QUSNBY 2,217.9293

RECEIVER TUNING GKV'R'L Fild Jari. 3. 195@ 6 Sheesishemf; 4

' @GVG Og@ 5J BY www ATTORNEY 0% 8, 1940- E. J. QUINBY l 2,217,293

RECEIVER TUNING ONTROL mad Jan. s, 1936 e sheets-snm 5 I v///////////////// mam-'/M/z ida-NL,

. ATTORNEY Oct. 8, .1940, E. J. QulNBY 2,217,293

RECEIVER TUNING CONTROL Filed aan. 5, 1936 efsneets-shen s INVENTOR EDM/0V J. OUI/V37 ATTORNEY Patented Oct. 8, 1940 PATENT OFFICE RECEIVER TUNING CGNTROL Edwin Jay Quinby, Yonkers, N. Y., assignor to Radio Corporation of America, a corporation' of Delaware Application January 3, 1936, Serial No. 57,354 I 23 Claims.

My present invention relates to radio receiver tuners, and more particularly to novel and improved arrangements for accurately adjusting, in a simple manner, the tuning device of a radio receiver of the superheterodyne type.

There has been disclosed by D.y E. Foster, in application Serial No. 55,749, led December 23. 1935, Patent No. 2,189,282, issued Feb. 6, 1940, an instantaneous station selector device in mechanical association with the adjustable tuning device of a radio receiver of the superheterodyne type; the selector being adjustable to different positions corresponding to predetermined station settings of the receiver tuning device, and an automatic frequency control (hereinafter referred to as AFC) network in the receiver functioning to remove the necessity for mechanical accuracy imposed by modern superheterodyne receiver selectivity. In general, said application discloses, and claims, a superheterodyne receiver equipped with AFC, and a station selector dial mechanism which is mechanically coupled with the 'tuning condenser device; a control switch being located at a fixed reference point with respect to the selector dial, and functioning to render inoperative the AFC during a relatively small portion of the dial rotation in order to eliminate the tendency of the AFC to cause a shift in the local oscillator frequency to an extent that one carrier will cause response to the exclusion of other carriers. In one of the modifications shown in the said application, the selector dial is provided with spaced station buttons, the buttons having pins adapted to mechanically cooperate with a member functioning not only to actuate an AFC regulation switch, but also as a dial rotation stop device.

It may be stated that it is one of the main objects of the present invention to provide in a superheterodyne receiver equipped with AFC,. a station selector mechanism adapted to actuate the tuning device of the receiver;v and the selector mechanism generally comprising a rotatable dial provided with depressible push buttons spaced evenly and symmetrically around the periphery of the dial, and each push button having associated therewith an eccentric stop-pin which may be adjusted to evenly, yor unevenly, spaced locations so as to engage a dial stop member in such a manner that the tuning device of the re ceiver may be adjusted to preselected station frequencies.

Another important object of the invention is `to provide a station selector mechanism for the tuning device of a radio receiver, wherein the (Cl. Z50-20) selector mechanism is of the dial type and is capable of varying the angular position of the adjustable elements of the tuning device through 180, but the dial being adjustable through 360; the rotatable dial, moreover, being provided with a plurality of spaced buttons, each of which has an eccentric dial rotation stop-pin which can be adjusted to operate through any one of a plurality of circularly arranged apertures provided in a plate spaced from the rotatable dial, and the function of the rotatable dial and spaced plate being to permit ready re-calibration of the push buttons when the receiver is moved .from one broadcasting area to another area having entirely different broadcasting stations.

Another object of the invention is to provide a station selector dial, having depressible dial rotation stop-pins spaced around the periphery of the dial; wherein the dial is directly coupled to the rotor shaft of the variable tuning condenser, and the stators and rotors of the tuning condenser being of such relative design that the stop-pins associated with the rotatable dial can be spaced substantially around the periphery of the dial.

Still other objects of the invention are to improve generally the eiciency, and flexibility in commercial usage, of an instantaneous station selector mechanism for superheterodyne receivers equipped with AFC, and more especially to provide such selector mechanisms in a manner such that they may be economically and readily assembled in receivers.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims; the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawings in which I have indicated diagrammatically several mechanical embodiments whereby my invention may be carried into eiect.

In the drawings:

Fig. 1 schematically shows a superheterodyne receiving system embodying one form of the invention,

Fig. 2 is a front View of the station selector mechanism, of the type shown in Fig. 1 as viewed from the front of the radio receiver operating panel, y

Fig. 3 is a partial sectional view of the selector, taken along line 3-3 of Fig. 2 looking in the direction of the arrows, and with certain of the push buttons removed,

Fig. 4 is a detailed View of the AFC switch when in off position,

Fig. 5 is a front View of the AFC switch in closed position, a fragment of the push button carrier plate adjacent the switch, being shown,

Figs. 6a, 6b, 6c show, in section, one of the push buttons respectively in depressed; normal; and withdrawn positions,

Fig. 7 shows a fragment of the button carrier plate, and the manner of designing it,

Fig. 8 schematically shows, in perspective, a modified form of station selector mechanism,

Fig. 9 is a perspective view of a detail of Fig. 8.

Referring now to the accompanying drawings, wherein like reference characters in the different figures designate similar constructional and circuit elements, attention is first directed to Fig. 1 which shows in purely schematic manner a superheterodyne receiver embodying AFC, as well as a simplified and accurate manual tuning mechanism. rIhe receiving system shown in Fig. 1 is of the superheterodyne type employing AFC and AVC, and has been disclosed and claimed in apvthat the first stage may be a radio frequency amplifier, of one or more tubes, which generally precedes the mixer network.

The first detector output circuit, resonated to an operating I. F. of 175 to 465 k.c., is coupled to the I. F. tuned input circuit of the I. F. amplifier. The latter is followed by a double diode tube, which may be of the GHG type; this type of tube being provided with independent diode electrodes, and is designated by the numeral 2.

The cominon resonant input circuit 'I of tube 2, the latter functioning as the second detector network, has one side thereof connected to the diode anode 8, while the opposite side of the circuit is connected to the diode anode 9. The high alternating potential side of the output circuit 6 of the I. F. amplifier, is connected through blocking condenser l0 to the midpoint of the coil 'I' of input circuit 'i'. The mid-point II is connected to the junction of resistors I2 and I3; one side of resistor i2 being connected to the cathode 8 of diode 8 8', and one side of resistor I3 being connected to the cathode 9' of the diode 9 9'.

The condenser I4 is connected between cathodes 8 and and cathode 9 is grounded. The input circuit 'I is tuned to the operating I. F., and is reactively coupled to the output circuit 6, as designated by the reference letter M. The audio component of detected I. F. energy is transmitted to one or more audio amplifiers, and the latter may be followed by a reproducer, the audio energy being derived from the junction of resistors I2 and I3. The automatic volume control (AVC) connection is employed to apply the direct current component of rectified I. F. energy to the signal grids of the various pre-second detector tubes. The AVC connection is made to the junction of resistor I2 and I3, and the gain control potential is appropriately filtered before being applied to the gain control grids of the controlled tubes.

The AFC network involves the tunable tank circuit I8 of the local oscillator. As is well known, the variable tuning condenser 20, in the tank circuit I8, has its rotors mechanically uni-controlled with the rotors of the variable tuning condensers of the tunable signal circuits feeding lthe rst detector.

The dotted line 2I designates such mechanical uni-control means, such as a common rotor shaft; and the oscillator is tuned, at any setting of the shaft 2 I, to a frequency which differs from the frequency of the signal circuits by the operating I. F. Those skilled in the art are fully aware of the manner of employing padding condensers in the tank circuit I8 for maintaining the operating I. F. constant in value as the tuner 2| is varied through the operating frequency range, which may be, for example, the broadcast band of 500 to 1500 k.c.

The locally produced oscillations are impressed on the first detector tube in any desired manner, as by impressing them on the cathode circuit thereof. Oi course. it is not essential to the present invention to employ separate tubes for the mixer and oscillator functions; a pentagrid converter of the 2A7 type may be employed, in any well known manner, as a composite oscillatormixer stage. In any case, there is electrically associated with the tank circuit I8 a frequency control tube 22. The electrical connections between the plate circuit of tube 22 and tank circuit I 8 are such that an effective inductance is reected across the tank circuit.

Briefly, and without going into a detailed discussion of the specific connections between the frequency control tube and the tank circuit of the oscillator, it is pointed out that a resistor 23 and condenser 24 are connected in series across the tank circuit I8. If the resistance of resistor 23 is large compared to the reactance of condenser 24, currents through this series circuit will be substantially in phase with the voltage across the tank circuit.

The current passing through the condenser 24 produces a voltage across the condenser which lags the voltage across the tank circuit by substantially 90. This lagging Voltage is applied to the grid of control tube 22, and the latter is preferably of the high mu, high plate impedance type. The plate current flowing in connection 25 to tube 22, will be substantially 90 ahead of the voltage across the tank circuit I8, The current through the tuning condenser 20 lags voltage across that circuit about 90. Thus. any plate current flowing through connection 25 to tube 22 acts as though the current flowing in the variable tuning condenser 20 has been decreased.

In other words, the tube 22 produces an e'ective inductance effect on the tank circuit I8 by virtue of the connections just described. The magnitude of this effective inductance is a function of the mutual conductance of tube 22. The AFC connection 26 is made from the control grid of tube 22, through an appropriate filter resistor 26', to the cathode side of resistor I2. The mutual conductance of tube 22 is varied in dependence upon the magnitude of the direct current component of the differential rectified I. F. energy. The magnitude and polarity of the potential at the cathode side of resistor I2 determines the sense of magnitude variation of the effective inductance reflected across tank circuit I8 by control tube 22.

Without going into detail concerning the operation of the frequency discriminator network for producing the AFC voltage, it is pointed out that the direct current voltages taken off from between point 40 and ground are equal and opposed at I. F. resonance. However, and as` clearly explained in the aforesaid Seeley application, when the I. F. energy `applied to circuit 6 is of a frequency off resonance, AFC voltage will be applied to the control grid of tube 22 through the connection 26.

'I'he potentials at either end of coil I with respect to the mid-point II are 180 out-of-phase. If the center tap II is connected to the primary circuit 6, two potentials are realized; one of these maximizing above the center frequency (that is, the resonant frequency of both circuits 6 and 1), the other potential maximizing below this center frequency. These potentials are applied to a pair of rectifiers, such as the diodes in Fig. 1, and the resulting direct current voltages are added in opposition; the sum being equal to zero. The output load of the rectiers comprises resistors I2 and I3, of like magnitude, connected in series between the cathodes 8 and 9. If the frequency of the I. F. energy departs from the predetermined operating I. F., the sum of the rectified outputs of the two diode rectifiers combined in opposition will be some real value whose polarity depends upon the sign of the frequency departure.

This action is secured by virtue of the fact that when the primary and secondary voltages of a double tuned transformer, such as M in Fig. l, are added vectorially, the absolute magnitude of the resultant vector will be greater on one side of resonance than on the other; the voltages differing 90 in phase, of course, when energy of the resonant frequency is applied. If the AFC applied to the grid of tube 22 is positive (thereby overcoming some of the initial bias applied in the cathode circuit of that tube), its mutual conductance is increased. The amount of leading current flowing in connection 25 is thereby increased; which is the same as though the lagging current flowing through the variable tuning condenser 20 has been decreased. This, in turn, acts as though that condenser had been decreased in value, thereby causing the tuned frequency of tank circuit I8 to increase.

Assuming, now, that a signal impressed on primary circuit 5 is approaching the I. F. value of 465 k. c., but is less than the latter, and also yassuming that point 40 has a positive potential with respect to ground; the grid of tube 22 will become positive, and increase the gain of the tube. This will result in an increase in the effective inductance reflected across tank circuit I8; and the frequency of the latter will increase. In this way, the frequency difference between the signal and oscillator circuits automatically is made to increase towards the desired I. F. value. Conversely, the frequency difference between the signal and oscillator circuits can automatically be made to decrease towards the desired I. F. value, as in the case where the signal energy applied to circuit 6 is departing from the operating I. F. and becoming greater in magnitude. The AFC action commences as soon as a` little of the side band energy of a modulated carrier wave is applied to the primary circuit 6. The polarity of the AFC voltage at point 4I), with respect to ground, depends on the phase of the coupling M. By way of example, it is pointed out that in Fig. 1, the coupling M is phased so that point 40 becomes positive with respect to ground when the applied signal is lower than the desired center frequency.

It is to be clearly understood, however, that the aforegoing description of the receiving system shown in Fig. 1 may be replaced by the type of AFC receiving system shown in Fig. 1 of application Serial No. 4,793, filed February 4, 1935, by C. Travis. In the latter type of system, mistuned I. F. rectifier circuits are employed; the rectifiers being differentially connected. The rectifiers are mis-tuned by like frequency values on either side of the operating I. F., and the mean direct current output of the rectifiers is used to vary the grid bias of an electron discharge tube, operating as an oscillator frequency control tube, in a sense such that a varying electrical characteristic of the control tube causes the tuning of the local oscillator to shift in that direction which will cause the IjF. energy to approach the operating I. F. value.

As pointed out in the aforesaid Foster application, the switch 30 functions to ground the AFC voltage derived from point 4U, and renders the AFC network inoperative at the will of the operator. This offers a means for correlating the operation of the AFC network with the tuning operation so as to render the tuning of the receiving system not only accurate, but highly simplied. This is necessary to overcome a practical difiiculty encountered when employing AFC in a superheterodyne type of receiver. This difficulty resides in the problem of dislodging a strong signal to make way for a weaker one on a closely adjacent channel, without having the weaker station jump right across the band to disappear on the other side. The switch 30 is supplemented by an auxiliary switch SI, the latter comprising a relatively fixed contact element 32 and a relatively movable Contact element 33. The contact element 32 is connected by lead 34 to theAFC line 25, whereas the contact element 33 is grounded. In actual practice, the switch 30 may be mounted in the rear of the receiver chassis, whereas the supplementary switch 3I may be mechanically associated with the selector dial as shown in further detail in Fig. 3.

The station selector mechanism that is employed is of the dial type. In general, it comprises a rotatable disk 40 which is provided with a plurality of station selector buttons 4I. Each of these buttons is depressible; a pin 42 being projected from the rear side of the selector dial upon button depression. Each projected pin 42 has a path of revolution such that it comes into contact with the edge of a pivoted switch closure member 43; the latter being limited in rocking motion between a pair of stops 44 and 45. The upper' edge of member 43 is relatively wide, and functions as a cam in such a manner that the AFC switch 3I is closed in either of the limiting positions of the member 43.

In other words, when the disk 4I) is rotated in one direction, a push button 4I being depressed, a pin 42 will move the toggle cam member 43 in the direction of rotation of the disk. Conversely, when the latter is rotated in the opposite sense, then a pin 42 will shift the cam 43 in the opposite direction. Regardless of the rotational sense of disk 40, contact between a pin 42 and cam 43 will result in the grounding of the AFC line 26 through the path including lead 34; contact elements 32 and 33; and ground. The selector disk 4@ may be coupled mechanically to the unicontrol adjusting means 2I through any desired mechanical coupling arrangement. For example, a 2:1 reduction gear ratio is shown employed mechanically to couple tuner 2| to the rotatable disk 40.

The reduction gearing comprises a small drive pinion 46 meshing with driven gear 41. The latter in turn has a rigid connection to the tuning element 2|.

In general, therefore, it will be seen that the manually adjustable tuning device of the receiving system comprises a rotatable station selector disk provided with a plurality of independent station selecting devices 4|. The actual tuning process involves the insertion of the users finger in the bore housing of a button 4|, assuming the button has been depressed, and the rotation of the dial 40 with its plurality of buttons. The rotation ceases when the selected pin 42 moves into contact with the toggle cam 43, and the latter rocks into contact with one of the stop pins. This results in the AFC becoming inoperative at that point, as well as in a positive arresting of the rotation of the selected dial. The chosen button 4| is then released thereby withdrawing pin 42, and with consequent opening of switch 3|.

The constructional details of the selector dial and its plurality of push buttons will now be considered. Particular attention is directed to Figs. 2 to '1 inclusive for these details. In Fig. 2 there is shown the appearance of the station selector mechanism as viewed from the front of the operating panel of a radio receiver. The selector dial 40, as shown more clearly in Fig. 3, consists of a shallow, cylindrical shell; its vertical exposed face being provided with a plurality of equidistantly spaced apertures U disposed in a circle concentric with, and adjacent to, the periphery of the said exposed face. The depth of the selector shell is such that it is capable of housing the various push buttons, the station kilocycle dial 5|, and the relatively stationary index arm 52. The shell 4D is rigidly secured to a base-plate 53 which is circular in shape, and of a diameter equal to that of the shell.

The plate 53 is provided with a hub 54, integral therewith, on its rear face; the hub 54 having a cylindrical projection 55. Furthermore, the plate 53 is provided on its front face with a relatively longer hub 56 which widens out at its extremity into a disk 51 having a diameter substantially equal to the diameter of a circular opening 58 in the exposed face of the selector shell. The scale 5| is secured to the exposed face of disk 51, and the periphery of the scale 5| is provided with kilocycle indicia 59 along the peripheral portion of scale disk 5|. As clearly shown in Fig. 3, the elements 55, 54, 56 and 51 are provided with a common bore 60; in which is disposed the horizontal portion 6| of the index arm 52. The rear portion of horizontal section 6| is rigidly secured, by any desired means, to a support plate 62.

The projecting portion 55 functions additionally as a stub shaft for the selector assembly, and this is accomplished by providing a bore 63 in the plate 62 and disposing the projection 55 in the bore. It is to be understood that the plate 62 is maintained in relatively fixed position With respect to the selector assembly, the means for maintaining the plate 62 in such immobile condition not being shown. The projection 55 also functions as a support for the pinion 64, the plate 62 being spaced from the rear face of circular plate 53 a distance sufficiently great to accommodate the reduction gearing and the tog gle cam. The pinion 64 is pinned to hub 54 so that the pinion can rotate with the selector assembly; the driven gear 65 is rigidly secured to the variable condenser rotor shaft 66. Those skilled in the art Will readily understand that the shaft 66 corresponds to the dotted line 2| in Fig. 1. The numeral 61 denotes the variable tuning condensers, and these will take the customary constructional form. Condenser 61 comprises the tuning condensers and 2U of Fig. 1.

The variable condenser 61 may be of the conventional bath tub type; the latter permitting only 180 of rotation of the rotors. It is because of this fact that it is necessary to utilize a 2:1 reduction ratio between gears 65 and 64. This reduction gearing ratio enables the push button apertures 50 to be distributed throughout the entire 360D on the exposed face of the selector shell. The rotor shaft 66 is provided with a driven pulley 68, the latter being coupled by belt 69 to a drive pulley 10; the latter is rigidly secured to a shaft 1| one end of which projects through an opening in the operating panel 12 of the radio receiver. The exposed end of shaft 1| is provided with a knob 13. It is to be understood that the knob 13 and its associated mechanical coupling to rotor shaft 66, is provided so that the user can readily calibrate the selector mechanism; or, if the receiver is of the multi-range type, to enable the user to adjust the receiver tuning device in such operation of the receiver Where it is not desired to resort to the selector dial.

The operating panel 12 is only partly shown, but it will be observed that the base of the selector shell is disposed within a relatively wide aperture, of circular configuration, provided in the panel. This wide aperture bears the reference numeral 14, and the periphery of aperture 14 is spaced from the periphery of the shell base 53. Bolt 15 rigidly aflixes the selector shell to the base plate 53, and three such bolts are shown in Fig. 2. It will now be appreciated that when the selector dial 40 is rotated the rotor shaft 6E will be rotated by Virtue of the coupled gears 64-65. Of course those skilled in the art will recognize that the portion 55 of the base plate 53 will De arranged within the bore 63 of the support plate 62 so that it will not slip sidewise; to preserve simplicity of disclosure this has not been shown.

In order to automatically stop the selector' dial 4U in its rotational movement at the same fixed reference point the toggle cam device is provided. In Fig. 4 there is shown a detailed View of the toggle cam and its associated AFC switch. The cam device generally comprises a pivoted element 16 having a configuration as shown in Fig. 4; the latter is best described as comprising a plate having a pair of substantially triangular portions joined at their apices, and the lower portion being of a relatively wider area than the upper one. Because of this shape the upper portion of the pivoted plate 16 functions as a cam, and the relatively narrow intermediate portion 16 functions to contact the rotation stops 45 and 44. The toggle cam 16 is secured for pivotal movement with respect to the forward face of plate 62 by securing the upper portion thereof to the plate 62 by means of a bolt-pivot fin 11. The head of pin 11 is substantially in alignment with the spacing at the upper peripheral edge of base plate 53.

The horizontal upper edge of the toggle cam is normally in contact with a resilient strip 8G; this strip being spaced from contact elements 33 and 32 of the AFC switch 3|. As shown in Fig. 4 each of strips 80, 33, and 32 have their ends positioned flxedly, and in spaced relation between insulation spacers 8|, the various spacers being bolted together by bolts 82. The free end of strip 88 is provided with an insulation spacer 83 which is secured to the strip 80, and which is normally in engagement with the under face of strip 33. The opposing faces of contact elements 33 and 32 are provided with contacting points 84, and it will be understood that when these points 84 contact the circuit from lead 34 to ground is complete. 'I'he ends of strips 32 and 33 which project beyond spacers 8| furnish the connection points to ground and lead 34.

The elements 80, 33, 32 are constructed of resilient material; for this reason the pivoted member 16 will be readily restored to normal position due to the downward pressure of the spring contact elements upon the top edge of the member 16. When a pin is moved out of contact with the vertical edge of member 16, the latter will be shifted into normal position. Each of the depressible push-buttons is provided with a spring-actuated plunger 85; the latter being integral with the head 86, but is arranged in parallel spaced relation with the plunger 85.

In Figs. 6a, 6b and 6c, there is shown the appearance of a push-button in respectively depressed, normal andwithdrawn positions. The detailed construction of the button is clearly shown; it will be observed that disc 53 is provided with a plurality of equidistantly spaced plunger cylinders 88 integral therewith. These cylinders are arranged in a circle whose plane is parallel to the plane of the circle of openings 50. The cylinders 88 project towards the dial 4|), as' shown in Fig. 3; and each cylinder is provided with an open end 89 in the rear face of disc 53, and an opposite end 98 having an aperture of a diameterr equal to that of plunger 85.

The depth of each cylinder 88 is such that when the button head 86 is completely depressed, as in Fig. 6a, the free end of pin 81 projects a sufficient distance beyond the rear face of disc 53 to strike cam member 16 when the dial is rotated. Surrounding each cylinder 88 is a circle of spaced bores 9|; these boresl being provided in the body of plate 53. Each pin 81 is arranged for reciprocation through any of bores 9| of its associated circle of such bores.

Each circle of bores permits selective adjustment of an associated pin 81 to a desired dial rotation stop position, To permit ready projection of a pin 81, as well as easy adjustment thereof, each plunger 85 is provided with a plunger head 92; opposed springs 93 and 94 being associated with the plunger. The spring 93 is disposed between the plunger head 92 and the shoulder 90 of the plunger casing. The spring 94 is disposed between the button head 86 and shoulder 90. The two opposed springs keep a button in the normal, or midway, position shown in Fig. 6b, until the 'button is depressed for operation, as in Fig. 6a; or is withdrawn, as in Fig. 6c, for adjustment. The threaded plunger head 92 prevents a button from leaving its central location accidentally, or otherwise, until the head is removed.

In this way, a smooth restoring movement is applied to each button after depression, or after re-calibration withdrawal of a pin 81. Each button head 86 may be provided with a station indicia-bearing disc 95; a securing ring 96 can be usedto maintain a disc 95 in exposed position on head'86. In Fig. 3, only one push-button is shown positioned between the plate 53 and the selector shell. It is to be understood that the remaining push-buttons have been removed from the remaining cylinders 88. Considering Fig. 2, it will be understood that each of apertures 5U hasfa plunger cylinder 88 in co-axial alignment therewith.

In Fig. 5, there is shown a detailed View of the relations of certain of the elements. The support plate 62 is. shown with its driven gear 65; the pinion 64 being shown cut away from hub 54 of plate 53. The support plate 82 is shown in fragments to denote that the spacing between driven 65 and cam member 16 may depend on the set designer.

This figure, further, shows a fragment of circular plate 53; only a single push button being:

disposed on the plate. Three cylinders 88 are shown; the circle of bores 9| associated with each plunger cylinder is also shown. The middle cylinder has a push button positioned therein; the

relation between the head 86 thereof and the circe of pin-bores 9| being illustrated.

The pin 81 is disposed within one of the bores, and the pin position is shown when the pin is in contact with the lagging edge of cam member 16. The leading edge of the cam member is in contact with the stop pin 44. The AFC switch is closed because of the upward pressure on contact strip 33 by the strip 88 and spacer 83 under thel iniiuence of the rising top edge of cam member 16. When the finger of the set user is withdrawn from the push-button head, the pin 81 is retracted; the cam member 16 thereupon assumes its normal position shown in Fig. 4. The- AFC switch elements, then, assume the positions shown in the latter figure.

From Fig. 5, it will be appreciated that each circle of rbores 9| functions to provide a plurality of possible stop positions for each pin 81. Eleven such positions are possible for each pin 81; this follows from the fact that each circle includes eleven bores, In designing the stop device for the selector dial, it is necessary to have the pivotable switch closure cam member 16 shifting in accordance with the direction of rotation of the dial 46. This assures the tuning shaft coming to rest in the same location regardless of whether the direction of rotation is clockwise or counter-clockwise. Mechanically, this action is secured by permitting the member 16 to be displaced from its normal, or center, position a distance equal to the radius of the cam actuating means. Since this last means is a pin projected by a depressed button, the radius is that of the pin.

The manner of laying out the bores 9| in circular plate 53 is shown in Fig. '7; it will be understood that the plate sector chosen for illustration is representative of the remainder of the plate. The three circles of bores 9| are shown having in association therewith their respective depressible push-buttons, It will be seen that the bores 9| in each circle are unevenly spaced; this results from the method employed in arranging these bores. Due to the 2:1 reduction gearing, it is possible to utilize the entire 360 of the exposed face of dial'40, as well as that of plate `53. In Fig. 2, there is shown utilized eighteen buttons; each of them corresponding to a desired station designation, as well as to a particular one of bore letters A to R. In Fig. 7 is shown-bore circles R-A-B; it will also be observed that these correspond to stations WABC; WJZ; WOR respectively in the New York city area.

It will be observed that each circle of bores includes diametrically opposed bores which are common to next preceding and following circles.

These pairs of bores are denoted by the designation Considering, now, the circle of bores designated A, it will be noted that the bores are alternated on either side of the line through opposed bores Thus, bores designated |-3- 5 1-0 are on one side oi this imaginary line; bores 2-468 are on the other side. This arrangement is true of each of the remaining circles. The position of each of the bores of a circle is accurately determined by the intersection of radial lines |00 (radiating from the center of circular plate 53) with a circle (dotted line 0 having as its radius the distance from the center of a button head to the vertical central axis of its pin.

The radial lines |00 are spaced at intervals of 2; hence the diameter of each circle of bores occupies 20. It will `now be seen that bore of circle A has its center at the intersection of the 352 radial line and dotted circle |0|; bore 2 occurs at the intersection of the 354 radial line and circle |0|; the remaining bores being determined similarly. It is because of this method of determining the location of the bores that they are distributed substantially over the circle |0|. There is thus assured a maximum number of pinreceiving bores 9| in a given circle with minimum crowding. By having the common bores 1:, it is possible to have a maximum number of bore circles around the periphery of plate 53, and yet not sacrice any of the bores 9 I.

' It will now be appreciated that the pin 81 of each push-button can be arranged in a plurality of possible positions; depending on the bore 9| selected when the button is in the position shown in Fig. 6c. This device assures ready calibration of the selector mechanism at the factory. Further, a sufficient number of stop positions are provided to enable the selector mechanism to be re-calibrated when the set is moved into a diierent broadcasting service area. In Fig. '7 there is shown the different settings of the three pins of the buttons assigned to bore circles R-A-B.

The manner of using the simplified and accurate tuner disclosed herein, should be clear from the drawings and the above description. To recapitulate, if it is desired to tune the receiver to a different station, the user places a finger tip on a button head (see Fig. 3) and presses down. The dial is then rotated in clockwise, or counterclockwise, direction until the projected pin 81 strikes cam member 1S and shifts it in the same sense; a stop pin arrests the rotation of the dial. At this arrested point of the dial, the rotor shaft is adjusted close to the setting required to tune in the desired station.

Further, the AFC switch 3| is simultaneously closed thereby rendering the AFC network ineffective; the receiving system now being in normal tuning state. The set user, then, removes the nger tip from the button head; the pin 81 is retracted thereby permitting cam member 16 to return to normal position and open the AFC switch 3|. The AFC accurately completes the tuning of the receiver by automatically adjusting the local oscillator in the manner previously explained. If it is desired to re-set one, or more, pins 81, it is only necessary to remove the selector shell 40; withdraw a pin 81 as shown in Fig. 6c, and rotate head 85 to shift the pin any desired one of bores 9|.

The reduction ratio gearing may be eliminated from the coupling between the selector mechanism and the rotor shaft. In Figs. 8 and 9 there is shown a modification of this invention wherein a direct mechanical coupling is utilized between the selector mechanism and the rotor shaft. In spite of this direct coupling, it is possible to distribute the dial rotation stop buttons over a major portion of the exposed dial face. This is accomplished by a special design of the stators and rotors of the variable condenser. As shown schematically in Fig. 8, the selector mechanism 40 is aiiixed to the rotor shaft 20| of the variable condensers. The latter is directly and rigidly aflixed to the base plate 53 (not shown) of the selector mechanism. It will be clearly understood that the construction of the selector mechanism is substantially the same as that previously described, except for the distinctions to be described in the following portion of the description.

The push buttons are equidistantly spaced around the periphery of the exposed face of the selector dial, but a relatively wider spacing occurs between the iirst and last of the push buttons, this wider spacing being substantially 40. In other words, the push buttons are disposed through 320 of the periphery of the exposed face of the rotatable dial 40.

The angular distribution of the push buttons is determined by the design of the rotors and stators of the ganged variable condensers. The rotors 202 generally are spiral in shape to provide a proper distribution of frequency (capacity) throughout the major portion of the selector dial circle. As shown, the rotors mesh with the sta.- tors through an angular distance of 320. In other words, the rotor shaft, in this form of the invention, is capable of continuous rotation in clockwise, or counter-clockwise, direction. This permits dialing in either direction throughout the entire compass of the selector mechanism. Due to the fact that the prole of each rotor is cut to have a spiral shape, there is a gradual change in capacity value from one end of the tuning scale to the other end, with a comparatively sudden return `to maximum, or minimum, capacity throughout a small sector. The 40 spacing between the first and last buttons of the selector mechanism 40 corresponds to this last named small sector. To maintain maximum capacity, as required in a condenser of present day design, the spiral rotors may be of greater radius, or greater in number, or both.

It will now be appreciated that by means of the variable condenser design shown in Fig. 8, it is possible to utilize a major portion of the dialing circle of the selector mechanism, and yet have a direct mechanical coupling between the condenser rotor shaft and the condenser mechanism.

The advantage of this construction resides in the fact that it is not necessary to sacrice any frequency settings since the rotors may be readily adapted for the operating frequency scale in any broadcasting area. The modication in Fig. 8 also shows a novel mode of illuminating the frequency scale 59 of the selector mechanism. 'I'he index arm 52 is maintained relatively xed with respect to the rotatable selector mechanism by having the rotor shaft 20| hollow, and disposing within the interior thereof a tube 203.

The tube 203 functions as an insulation sleeve between the hollow metallic condenser shaft 20| and an electrical conductor 204 which is run through the insulation sleeve 203. A member 205, shown in detail in Fig. 9, functions as an anchor for the index arm 52, the insulation sleeve 203, and the dial illuminating lamp 200. In other words, when the selector dial 40 is rotated, the hollow shaft 201, carrying the rotors 202, is rotated with respect to the relatively xed sleeve 203 and axial conductor 204. The anchor 205 maintains the conductor and sleeve fixed with respect to the rotor shaft 20 I. Those skilled in the art will readily understand that the socket of lamp 206 may be secured to the conductor 204 in any well known manner, and that a brush 201 may be utilized to make electrical contact between the socket and the illuminating lamp and the grounded rotor shaft 20L The dial scale pointer 52 can be rigidly secured to the conductor 204 in any well known manner, and because of this construction, the pointer and illuminating lamp will be maintained relatively fixed with respect to the rotatable dial 40.y

In order to preserve simplicity of disclosure, the details of the coupling between the rotor shaft 20| and the selector mechanism have not been shown. However, it will be understood that the rotor shaft 20| may be rigidly affixed to the hub 54 of circular plate 53, and that the sleeve 203, and its axial conductor 204 may be run through the bore thereby permitting the pointer 52 and illuminating lamp 60 to be disposed as shown in Fig. 8.

In actual usage, the operation of the modification shown in Fig. 8 is the same as that explained previously in connection with the form shown in Fig. 2. The station indicia on the eX- posed heads of the push buttons, in either modiiication, may be made of material which glows in the dark, such materials being well known; thereby facilitating adjustment of the selector dial in the darkness as for example in the case of an automobile radio receiver employed in night driving. Again, the station indicia may be in raised characters, or Braille, so that blind persons may easily use the mechanism. Furthermore, while it has been stated that the dial 40 is positioned on the operating panel above the tuning knob 63, it is within the scope of this inven* tion to dispose the selector dial at the side of the cabinet for aesthetic reasons. Furthermore, if it is desired to keep the Selector dial on the front panel, and if for design purposes it is desired to keep the dial normally hidden from view, a slidable, or pivotable, door may be used to cover the selector dial.

While I have indicated and described several arrangements for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular constructions shown yand described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is:

l. In combination with the adjustable tuning device of a radio receiver, a rotatable station selector disc arranged to vary said tuning device to different station reception positions, a plurality of independent finger `positioning devices mechanically associated with said disc, means, relatively xed with respect to said rotatable disc, for stopping the rotation of said disc upon adjustment of a selected one of said devices to a fixed reference point, and additional means, iixedly spaced from said positioning devices and disc, provided with a plurality of means for each positioning device for securing independent adjustment of any 'of said positioning devices to a predetermined disc stopping point.

2. In combination with the adjustable tuning device of a radio receiver, a rotatable station selector disc arranged to vary said tuning device to different station reception positions, a plurality of independent finger positioning devices mechanically associated with said disc, means, relatively fixed with respect to said rotatable disc, for stopping the rotation of said disc upon adjustment of a selected one of said devices to a fixed reference point, and a plate, fixedly spaced from said selector disc and devices, provided with a plurality of means for each positioning device for securing independent adjustment of each of said positioning devices.

3. In combination with the adjustable tuning device of a radio receiver, a rotatable station selector having a mechanical coupling to said tuning device for variation of the latter to different station reception positions, a plurality of independent depressible push buttons mechanically associated with said disc, each of said buttons being provided with a vdial rotation stop pin, a member arranged to rock between a pair of limiting points upon being contacted by a depressed button pin, and a plate disposed between said last member and said selector disc, said plate being provided with a plurality of groups of apertures arranged to correspond to said stop pins and each group of apertures being adapted to calibrate its respective stop pin to different dial rotation stop positions.

4. In combination with the adjustable tuning condenser of a radio receiver, a rotatable station selector disc arranged to vary said condenser to different station reception positions, a plurality of independent finger positioning devices mechanically associated with said disc, means relatively iixed with respect to said rotatable disc for stopping the rotation of said disc upon adjustment of a selected one of said devices to a fixed reference point, each of said positioning devices comprising an eccentric stop pin and a plate spaced from the disc provided with a plurality of groups of pin calibration bores, each pin being associated with one of said groups.

5. In combination with the adjustable tuning` condenser of a radio receiver, a rotatable station selector disc arranged to vary said condenser to different station reception positions, a plurality of independent linger positioning devices mechanically associated with said disc, means relatively fixed with respect to said rotatable disc for stopping the rotation of said disc upon adjustment of a selected one of said devicesto a xed reference point, each of said positioning devices comprising an eccentric stop pin, and means comprising a plate provided with a plurality of groups of pin receiving bores, each group of bores being associated with a corresponding pin for adjusting said eccentric stop pins to evenly or unevenly spaced locations.

6. In combination with the adjustable tuning condenser of a radio receiver, a rotatable station selector disc arranged to vary said condenser to different station reception positions, a plurality of independent finger positioning devices mechanically associated with said disc, means relatively fixed with respect to said ro tatable disc for stopping the rotation of Said disc upon adjustment of a selected one of said devices to a fixed reference point, each of said positioning devices comprising an eccentric stop pin, said stopping means comprising a pivotable cam disposed in the path of movement of the pins and being caused to shift between a pair of limiting positions in accordance with the direction of rotation of said disc, each of said eccentric stop pins being adapted to rock said cam when the dial is rotated to a point such that a selected pin contacts said cam, and additional means, including a group of positioning bores associated with each pin, to adjust each of said stop pins to a plurality of spaced locations thereby to engage the cam at different points thereof.

7. In combination with a variable tuning condenser of a radio receiverl a rotatable station selector dial, means mechanically coupling said dial to the rotor shaft of said condenser, a plurality of spaced depressible station buttons disposed on said dial, each of said buttons being provided with an eccentric stop pin, a plate spaced from said dial and provided with a plurality of groups of bores, each group corresponding to a given one of said stop pins, each of said bores of a group being adapted to receive its respective stop pin, and means, relatively fixed with respect to said rotatable dial, for stopping the rotation of said dial upon contact therewith of the stop pin of a depressed one of said buttons.

8. In combination with a variable tuning condenser of a radio receiver, a rotatable station selector dial, means mechanically coupling said dial to the rotor shaft of said condenser, a plurality of spaced depressible station buttons disposed on said dial, each of said buttons being provided with an eccentric stop pin, a plate spaced from said dial and provided with a plurality of bores corresponding to said stop pins, each of said bores being adapted to receive its respective stop pin, and means, relatively fixed with respect to said rotatable dial, for stopping the rotation of said dial upon contact therewith of the stop pin of a depressed one of said buttons, and said spaced plate being provided with at least one auxiliary bore adjacent each of the aforesaid bores thereby to provide variation in the angular distances between the centers of adjacent eccentric pins.

9. In combination with a variable tuning condenser of a radio receiver, a rotatable station selector dial, means mechanically coupling said dial to the rotor shaft of said condenser, a plurality of spaced depressible station buttons disposed on said dial, each of said buttons being provided with an eccentric stop pin, said dial being provided with a series of bores circularly arranged about each station button, the eccentric stop pin of each station button adapted to cooperate selectively with any one of the associated series of bores whereby individual adjustment of the station buttons is provided, and means, relatively fixed with respect to said rotatable dial, for stopping the rotation of said dial upon contact therewith of the stop pin of a depressed one of said buttons, a pair of opposed springs mechanically associated with each of said push buttons constructed and arranged to maintain each button in a position such that its associated stop pin is normally outI of the path of contact with said dial stopping means.

1G. In combination with a radio receiver of the superheterodyne type embodying an adjustable tuning device, automatic frequency control means, responsive to received signal energy, for adjusting the local oscillator frequency to a magnitude such that the frequency of the intermediate frequency energy is made to approach the operating frequency value, switch means for rendering the frequency control inoperative, an adjustable station selector mechanically coupled to the tuning device to vary the position thereof,

said tuning device comprising a variable condenser including a plurality of rotors and a plurality of stators, said rotors having their profiles cut in substantially spiral shape, and being arranged for rotation over 360 in clockwise, or counter-clockwise, sense, said selector being provided with a plurality of independent finger positioning devices for adjusting the selector to different desired settings of said rotors, and said switch means being disposed in the path of said devices in such a manner that the switch is actuated when a device is adjusted to a predetermined reference point.

1l. In a system of the type defined in claim 10, said selector' comprising a rotatable dial, and said positioning devices comprising spaced depressible push buttons provided around a portion of the periphery of the rotatable dial whose angular distance bears a predetermined relation to the active angular distance of said rotors.

i2. In a system as defined in claim l0, said rotors being disposed on a hollow rotor shaft, a relatively xed conductor disposed within said hollow shaft, and a scale illuminating means electrically associated with said conductor.

13. In combination, a variable tuning condenser of a radio receiver, a rotatable station selector drum, means mechanically coupling said drum to the rotor shaft of said condenser, a plurality of depressible station buttons carried by said drum and selectively operable to adjust the tuning condenser to desired station positions, each of said buttons being provided with an eccentric stop pin, said drum being provided with a series of bores circularly arranged around each station button, the eccentric stop pin of each station button adapted to cooperate selectively with any one of the associated series of bores whereby individual adjustment of the station buttons is provided, and means, relatively fixed with respect to said rotatable drum, for stopping its rotation at a predetermined position upon contact therewith of the stop pin of a selectively depressed button.

14. Selective adjusting mechanism comprising a manually-shiftable element and selectively operable stop means for stopping movement of said element when a desired adjusted position of said element is reached, comprising a plurality of stems depressible on said shiftable element, a stop on each stem relatively offset with respect to the stem and depressible therewith into stopping position, means normally urging each stem and its associated stop toward non-stopping position, said stem and its stop being turnable on the shiftable element whereby to index the stop on the element with respect to said stem, and guiding means on said element in position to cooperate with said stop means to hold the stop in its indeXed position.

l5. In a tuning control for radio receivers or the like having a tunable element, a manually operable rotatable member, means connecting said member to said tunable elementy said member having a series of angularly spaced openings and a plurality of additional angularly spaced openings concentric with said series of openings, a plurality of selectively operable control members slidably mounted in each of said series of openings, a plurality of stop lelements mounted on said control members for movement relative thereto, said stop elements being slidably and adjustably mounted in selected ones of said additional openings, and means cooperating with the selectively operated stop element to stop said rotatable member and said tunable element in a predetermined adjusted position.

16. Selective adjusting mechanism comprising a manually shiftable element and selectively operable means for stopping movement of said element when a desired adjusted position of said element is reached comprising a plurality of stems depressible on said element, a stop pin on each stern and depressible therewith into stopping position, means normally urging each stern and its associated pin toward non-stopping position, said element having a plurality of openings for the stop pin of each stem, said openings being laterally oiiset with respect to each other whereby each of said pins may be indexed in any one of a plurality of relatively oiset positions.

17. Selective adjusting mechanism comprising a manually shiitable element and selectively operable stop means for stopping movement of said element when a desired adjusted position of said element is reached, comprising a plurality of stems depressible on said shiftable element, a stop on each stem relatively offset with respect to the stem and depressible therewith into stopping position, means normally urging each stern and its associated stop toward non-stopping position, said stem and its stop being turnable on the shiftable element whereby to index the stop on the element with respect to said stem, and guiding means on said element in position to cooperate with said stop means to hold the stop in its indexed position, said manually shiftable element comprising an escutcheon plate of annular coniiguration and formed with openings opposite which said buttons are mounted in position to be depressed, as by the insertion of the finger of an operator in any of said openings for the purpose of shifting said element.

18. Selective adjusting mechanism comprising a manually shiftable element and selectively operable means for stopping movement of said element when a desired adjusted position of said element is reached comprising a plurality of stems depressible on said element, a stop pin on each stem and depressible therewith into stopping position, means normally urging each stem and its associated pin toward non-stopping position, said element having a plurality of openings for the stop pin of each stem, said openings being laterally offset with respect to each other whereby each of said pins may be indexed in any one of a plurality of relatively offset positions, wherein the manually shiftable element comprises an annular portion defining an opening, and indicator means in said opening for showing, at all times, the adjusted position of the mechanism.

191. Selective adjusting mechanism comprising a manually shiftable element and selective means operable during and as a part of the shifting of said element to stop the same when a desired adjusted position is reached, said selective means comprising a plurality of selectors individually and selectively depressible on said manually shiftable element, each depressible selector comprising a guide stem and a cooperating stem-like stop element axially movable on the manually shiftable element, means normally urging said guide stem and stop element toward inactive position on the shiftable element, and means forming a cooperating stop adapted to engage said stapelement when the selector is depressed on said shiftable element whereby to stop the shiftable element in a position determined by said stop element.

20. Selective adjusting mechanism comprising a manually shiftable element and selectively operable stop means for stopping movement of said element when a desired adjusted position of said element is reached, comprising a plurality of stems depressible on said shiftable element, a stop on each stem relatively offset with respect to the stern and depressible therewith into stopping position, means normally urging each stem and its associated stop toward non-stopping position, said stem and its stop being turnable on the shiftable element whereby to index the stop on the element with respect to said stem, and guiding means on said element in position to cooperate with said stop means to hold the stop in its indexed position.

251. In a tuning control for radio receivers having a tunable element, a manually operable rotor provided with a central opening, a station dial disposed in said opening, said rotor having a plurality of angularly spaced openings, a plurality of selectively operable push buttons slidably mounted in said openings, each of said push buttons corresponding to a diierent selected broadcast station, luminous means located centrally of said rotor adjacent said dial and being flxedly arranged relative to said rotor, and means cooperating with said selectively operable push buttons to stop said rotor in predetermined adjusted positions selectively to tune said receiver to stations represented by said push buttons.

22. Selective adjusting mechanism comprising a manually shiftable element and selective means operable during and as a part of the shifting of said element to stop the same when a desired adjusted position is reached, said selective means comprising a plurality of selectors individually and selectively depressible on said manually shiftable element, each depressible selector comprising a guide stem and a cooperating stem-like stop element axially movable on the manually shiftable element, lmeans normally urging said guide stem and stop element toward inactive position on the shiftable element, and means forming a cooperating stop adapted to engage said stop element when the selector is depressed on said shiftable element whereby to stop the shiftable element in a position determined by said stop element, said manually shiftable element comprising a wheel having a rim formed with channels in spaced relationship around said rim for receiving each the guide stem of a selector, said rim being formed with a plurality or guideways spaced apart around said rim and adapted to receive the stop elements whereby the stop element of each selector may be assembled in any one of a number of said guideways.

23. In a tuning control for radio receivers or the like having a tunable element, a manually rotatable member, means connecting said member to said tunable element, said member having a series of angularly spaced openings concentric to its axis of rotation and a plurality of additional angularly spaced openings, a plurality of selectively operable push buttons slidably mounted in each of said series of openings, a plurality of stop elements mounted on said push buttons for operation thereby, said stop elements being slidably and adjustably mounted in selected ones of said additional openings, a stationary member, and means having a predetermined movement relative to said stationary member and cooperating with each selectively operated stop element for stopping said rotatable member and said tunable element in a predetermined adjusted position independent of the direction of rotation of said rotatable member.

EDWIN JAY QUINBY. 

